Field of Invention
The invention relates to an air supply system on a vehicle, comprising a Tire Pressure Control System (TPCS) and an air dryer. More specifically, the invention concerns a means for drying air used within a TPCS on a tractor.
Description of Related Art
Vehicle air supply systems require air dryers to discharge humidity from the air before supplying it to consumers on a vehicle. Damp air can cause corrosion in pipes and other components on the vehicle, so before supplying air to consumers, or air reservoirs (for example, for the vehicle's brake system) the air is usually guided through a dryer. When the air is passing through the dryer to dry the air, this mode of operation is known as a drying mode.
Due to the restricted load capacity of dryers, a second operation mode, known as a regeneration mode is required which involves passing air through the reservoir in an opposite direction and discharging it to the atmosphere. A regeneration mode thus removes water deposited in, or on the drying material of the dryer.
It is known to use double chamber dryers which comprise two separate dryer reservoirs, so that if one chamber is drying the air from the compressor in a drying mode, the other chamber is in a regeneration mode. The shift between the two modes of each drying chamber is time-controlled, so that the dryer may continually be used to dry air.
Furthermore, Electrically Operated Air Dryers (EOD) are also known. These dryers only require one dryer portion and the shift between the two modes of operation, that is the switch between the regeneration mode and the drying mode is not time controlled by a control unit. The two modes are controlled by measuring the volume of air passing through the dryer by measuring the compressor time or measuring the pressure rise in the reservoirs (and knowing that a certain pressure rise requires a predetermined air volume). A percentage of the volume of air in the air supply system is then guided back for the regeneration.
Even if the usage of EODs reduces regeneration time, a percentage of the volume of air (approximately 12%) is still required for regeneration and is not available for the general air supply to components. For example, after drying 1000 liters of air within an air supply system, 12% of the volume, that is 120 liters must be used for regeneration. The efficiency of the system is therefore reduced.